Europe expected to see a large increase in Hurricane Sandy-like hybrid storms

Watch out, Europe. Dangerous part-hurricane, part extratropical hybrid storms like Hurricane Sandy of 2012 are expected to be an increasing threat for Western Europe by the end of the century due to global warming, said a team of scientists led by Reindert J. Haarsma of the Royal Netherlands Meteorological Institute. In a paper called "More hurricanes to hit Western Europe due to global warming", published in April 2013 in Geophysical Research Letters, the researchers describe the results from runs of a high-resolution (25 km grid spacing) climate model based on the European Centre for Medium Range Weather Forecasts (ECMWF) numerical weather prediction model. The model predicts that the breeding ground for Atlantic hurricanes will shift approximately 700 miles eastwards as the oceans warm this century. Hurricanes which form farther to the east can spend more time over warm tropical waters before turning north and northeast towards Europe, increasing the odds that these storms will have hurricane-force winds upon arrival in Europe. The model showed that wind shear will change little in the region over the coming decades, resulting in a large increase in storms with hurricane-force winds affecting Western Europe. Most of the these storms will not be tropical hurricanes upon arrival in Europe, but will be former hurricanes that have transitioned to extratropical storms. However, as we saw with Hurricane Sandy of 2012, these hybrid storms can be extremely dangerous. Summed over Norway, the North Sea, and the Gulf of Biscay, the model found that the number of hurricane-force storms in August - October increased from 2 to 13 over the 21st century, with almost all future West European hurricane-force storms predicted to originate as hurricanes or tropical storms in the tropics by 2100. The researchers conclude that "tropical cyclones will increase the probability of present-day extreme events over the North Sea and the Gulf of Biscay with a factor of 5 and 25 respectively, with far reaching consequences especially for coastal safety."

Europe's hurricane historyOnly once since accurate records began in 1851 has an actual hurricane with full tropical characteristics hit Europe. This happened on September 16, 1961, when Category 1 Hurricane Debbie hit northwestern Ireland. Wind gusts reached 106 mph at Ballykelly and 104 mph at Tiree and Snaefill, and coastal radio stations reported the airwaves were jammed with calls for help from small ships and fishing craft. Eleven people were killed and 50 injured in the storm. The only other tropical cyclone recorded to have hit Europe since 1851 was Hurricane Vince of 2005, which hit southern Spain as a tropical depression on October 11, 2005. Historical documents also suggest a hurricane hit Spain on October 29, 1842.

Figure 2. Hurricane Debbie of 1961 was the only fully tropical hurricane ever recorded to hit Europe.

Britain's history of ex-hurricane strikesHurricanes that transition to powerful extratropical storms hit the British Isles several times per decade, on average. In October 2014, after battering Bermuda, the remnants of Hurricane Gonzalo affected Europe as a powerful extratropical storm, bringing strong winds, torrential rain, and heavy snowfall in western, central, and southern portions of the continent. Three people were killed, and damages in Netherlands, Germany, and Slovenia were estimated at $42 million. In 2011, Hurricane Katia brushed by Newfoundland, made the transition from a tropical system to a powerful extratropical storm, and maintained strong winds of 50 - 65 mph as it crossed the Atlantic. Ex-Katia hit northern Scotland on September 12, 2011. Glen Ogle, Scotland, at an elevation of 1500 feet (546 meters), received sustained winds of 60 mph, gusting to 86 mph. Cairngorm, in the Scottish Highlands at an elevation of 4085 feet, reported sustained winds of 67 mph. With the trees in full leaf, tree damage was much higher than a winter or springtime storm of similar ferocity would have caused. One person was killed by a falling tree, and heavy tree damage and numerous power failures were reported throughout Britain. Other gusts experienced in Britain included 76 mph at Edinburgh Blackford Hill, 75 mph at Capel Curig in Wales, 72 mph at Glasgow Bishopton, and 71 mph at Loftus, North Yorkshire.

Figure 3. Image of Hurricane Katia taken from the International Space Station at 15 GMT September 9, 2011, by astronaut Ron Garan. At the time, Katia was a Category 1 hurricane with 85 mph winds. Long Island, New York is visible at the lower left.

Figure 4. Surface wind estimate from the Windsat satellite at 4:04 am EDT on Monday, September 12, 2011. The center of Extratropical Storm Katia is marked by an "L", and winds in excess of 50 knots (58 mph, purple triangles) were occurring to the southwest of the center, near the west coast of Ireland. Image credit: NOAA.

As reported by UK Met Office forecaster John Hammond in a post on the BBC 23 degrees blog, Britain has been affected at least eight times in the past twenty years by extratropical storms that were once tropical storms or hurricanes. Before Katia of 2011, the most recent such storm was Hurricane Bill of 2009, which hit Ireland as an extratropical storm on August 25 with sustained winds of 45 mph. Bill was a Category 4 hurricane northeast of the Lesser Antilles five days prior. In 2006, a record three extratropical storms that had once been tropical cyclones hit Britain:

Extratropical Storm Alberto, which had been a strong tropical storm that hit the Florida Panhandle, hit northern Ireland and Scotland as an extratropical storm with 35 mph winds.

Extratropical Storm Gordon hit Ireland on September 21, 2006, with sustained winds of 65 mph. Gordon brought record warm temperatures as tropical air pushed north across the UK, and also strong winds that brought down power lines in Northern Ireland. Wind gusts to 60 mph (97 km/h) occurred in the Isles of Scilly off the southwest coast, and 81 mph (130 km/h) on the mainland.

Figure 5. Path of Hurricane Lili of 1996, which caused $420 million in damage to the U.K. as an extratropical storm.

Other post-tropical cyclones that have the U.K. in the past twenty years include Hurricanes Isaac and Leslie of 2000, Hurricane Karl of 1998, and Hurricane Lili of 1996. The most severe of these storms was Extratropical Storm Lili, which hit Ireland on October 28, 1996, with sustained winds of 65 mph. Lili caused $420 million in damage (2011 dollars) in the U.K. According to Wikipedia, Lili produced a 92 mph (148 km/h) gust at Swansea, South Wales, while bringing a 4' (1.2 meter) storm surge that inundated the River Thames. In Somerset, 500 holiday cottages were severely damaged. A U.S. oil drilling platform, under tow in the North Sea, broke loose during the storm and nearly ran aground at Peterhead. On the Isle of Wight, a sailing boat was beached at Chale Bay; luckily all five occupants were rescued. It was the most damaging storm to have struck the United Kingdom since the Great Storm of 1987, which killed 22 and did $660 million in damage (1996 dollars.) However, Lili also broke a four-month drought over southwest England.

All but one of these storms hit during the peak part of hurricane season, mid-August - late October. The only exception was Ex-Tropical Storm Alberto of 2006, which hit Britain in June.

Figure 6. Hybrid subtropical storm of October 8, 1996, off the coast of Italy. According to Reale and Atlas (2001), the storm had characteristics similar to a hurricane, but formed over cool waters of 21.5°C (71°F.) They reported that "The maximum damage due to wind occurred over the Aeolian Islands, at 38.5°N, 15°E, to the northeast of Sicily: assistance for disaster relief was required. Unfortunately, no weather station data were available, but the media reported sheds, roofs and harbor devices destroyed, and houses and electric lines damaged, due to 'extremely strong westerly wind.' The perfect agreement between the observations at Ustica, the storm scale, the eye-like feature position and the damages over the Aeolian Island reasonably suggest that the hurricane-level intensity of 32 m/s (72 mph) was reached over the Aeolian Islands." A similar hybrid low affected Algeria on 9 - 10 November 2001. This storm produced upwards of 270 mm (10.6") of rain, winds of 33 m/s (74 mph), and killed 737 people near Algiers, mostly from flooding and mud slides. Image credit: Dundee satellite receiving station.

Hurricanes in the Mediterranean Sea?The Mediterranean Sea between Europe and Africa has experienced several damaging hybrid subtropical storms in recent decades, but has never experienced a fully tropical hurricane in recorded history. However, global warming may cause the Mediterranean to start spawning hurricanes by 2100, according to a 2007 study by a research team led by Miguel Angel Gaertner of the University of Castilla-La Mancha in Toledo, Spain. They ran nine different climate models with resolutions of about 50 km and found that some (but not all) of the models simulated hurricanes in the Mediterranean in September by the end of the century, when ocean temperature could increase by 3°C, reaching 30°C.

Though the Mediterranean may start seeing hurricanes by the end of the century, these storms should be rare and relatively short-lived for three reasons:

1) The Mediterranean is quite far north and is subject to strong wind shear from jet stream activity.

2) The waters are shallow, and have relatively low heat content. There is no deep warm water current like the Gulf Stream.

3) The Mediterranean has a lot of large islands and peninsulas poking into it, increasing the chances that a tropical storm would weaken when it encountered land.

* URBAN AND SMALL STREAM FLOOD ADVISORY FOR... SOUTHEASTERN SHERMAN COUNTY IN CENTRAL NEBRASKA... SOUTHERN HOWARD COUNTY IN CENTRAL NEBRASKA...

* UNTIL 1100 AM CDT

* AT 457 AM CDT...LOCAL LAW ENFORCEMENT OFFICIALS REPORTED THUNDERSTORMS WITH HEAVY RAINFALL ACROSS THE ADVISORY AREA. DOPPLER RADAR ESTIMATED 2 TO 3 INCHES OF RAIN HAD FALLEN ACROSS THE ADVISORY AREA.

* RUNOFF FROM THIS EXCESSIVE RAINFALL WILL CAUSE MINOR FLOODING TO OCCUR...ESPECIALLY ALONG SMALL STREAMS AND NEAR LOW WATER CROSSINGS. SOME LOCATIONS THAT WILL EXPERIENCE MINOR FLOODING INCLUDE RURAL AREAS OF SOUTHERN HOWARD AND SOUTHEAST SHERMAN COUNTIES...AND INCLUDING BOELUS...DANNEBROG...ROCKVILLE AND ST. LIBORY.

* LAW ENFORCEMENT REPORTED WATER COVERING ST. PAUL ROAD JUST SOUTH OF ST. LIBORY.

* TIMING...SNOW WILL CONTINUE THROUGH WEDNESDAY MORNING. THE SNOW WILL BE HEAVY AT TIMES.

* MAIN HAZARD...TOTAL SNOW ACCUMULATION OF 14 TO 21 INCHES.

* OTHER CONDITIONS...NORTHERLY WINDS OF 20 TO 30 MPH WITH HIGHER GUSTS WILL RESULT IN AREAS OF BLOWING SNOW REDUCING VISIBILITIES TO UNDER A QUARTER MILE AT TIMES. BRIEF PERIODS OF NEAR BLIZZARD CONDITIONS WILL BE POSSIBLE.

The greatest tornado threat today will be after dark, meaning residents in the 10% hatched region -- or anywhere where tornado probabilities have been outlined in this vicinity -- need to pay attention to the news media and have their weather radio on if accessible.

Low-level shear isn't strong per se, but it will get the job done. I wouldn't be surprised to see a strong to significant tornado or two later.

AS SUCH...DIURNAL RE-INTENSIFICATION OF FRONTAL CONVECTION APPEARS PROBABLE...WITH SEVERE INTENSITY BEING MAINTAINED INTO THE EVENING AND PERHAPS OVERNIGHT HOURS AS ACTIVITY DEVELOPS EWD. PRIMARY HAZARDS SHOULD BE ISOLATED TO SCATTERED DAMAGING WINDS ALONG WITH A FEW TORNADOES.

SPC has issued a Moderate risk for severe weather today for portions of central Oklahoma and northern Texas including the cities of Oklahoma City, Norman, Tulsa, and Wichita Falls, TX. The main threat will be large and destructive hail with many storms producing over 2 inch hail. Tornadoes are also going to be a major threat today and a few strong tornadoes could occur around the OKC area. Be safe!

Good morning. Potentially dangerous severe weather event today across parts of OK and TX where the moderate risk has been issued. Not looking like an outbreak but probably one of our busiest severe weather days this year so far. Large hail is the biggest threat, with a few tornadoes and possibly and isolated strong tornado also expected.

Good morning, everyone. Evening, Aussie. A balmy 66 degrees here with a high later of 82. The kids will get recess today as the rain has been pushed back to starting tomorrow afternoon. Now instead of just rain, it'll be severe weather. That's Spring for you.

.SYNOPSIS...AT MID AND UPPER LEVELS...HIGH PRESSURE WEAKENS ANDSHIFTS WEST AND TROUGHINESS WILL INCREASE OVER THE AREA INSLIGHTLY CYCLONIC FLOW WITH A BROAD TROUGH PASSAGE ON THURSDAY. A75 KNOT JET FROM THE NORTHWEST WILL CROSS THROUGH THE AREA SHORTLYAFTER...FOLLOWED BY A WEAKENING RIDGE SET TO PASS ON SATURDAYNIGHT AT UPPER LEVELS. LIMITED MOISTURE ONLY AT MID LEVELS THATBEGINS TOMORROW AND LASTS THROUGH FRIDAY WILL AID IN SCATTEREDSHOWERS.

AT LOWER LEVELS...MODEST HIGH PRESSURE IN THE WESTERN ATLANTICWILL MOVE INTO THE CENTRAL ATLANTIC LATE IN THE WEEK. ITSREPLACEMENT WILL MOVE INTO THE WESTERN ATLANTIC SUNDAY AND MONDAYTHUS KEEPING MODERATE TO FRESH TRADE WINDS THROUGH THE WEEK ANDINTO NEXT WEEK.

&&

.DISCUSSION...STRONGER SHOWERS SET UP OVERNIGHT OVER PUERTO RICOALONG THE SOUTHEAST AND NORTHEAST COASTAL PLAINS AND FOOTHILLS.SOME OF THE HIGHEST AMOUNTS WERE UPWARD OF 1 INCH...WITH ONE TENTHINCH FAIRLY COMMON JUST INLAND. THE BAND OF MOISTURE PRODUCINGTHESE SHOWERS IS MOVING ONTO THE PUERTO RICAN MAINLAND AFTERGIVING SOME SHOWERS TO THE U.S. VIRGIN ISLANDS AND WILL CONTINUEINLAND TO PROVIDE NUMEROUS SHOWERS IN THE WESTERN INTERIOR OFPUERTO RICO AND A SLIGHT CHANCE OF A THUNDERSTORMS THIS AFTERNOON.MOISTURE IS SHALLOW HOWEVER...SO HEAVY RAIN WILL BE QUITELOCALIZED. SOME AMOUNTS COULD EXCEED 1.5 INCHES. DRIER AIR MOVESIN ON THE TRADE WIND FLOW BY 10/00Z CLEARING ALL BUT A FEW OFTHESE SHOWERS OUT BY SUNSET. ANOTHER BAND OF MOISTURE WILL BRINGSIMILAR CONDITIONS ON WEDNESDAY AFTER WHICH MOISTURE IS SLIGHTLYLESS AND SHOWERS SHOULD BE LIMITED TO SCATTERED UNTIL SUNDAY.LITTLE CHANGE IN THE SURFACE SYNOPTIC PATTERN OVER THE LOCAL AREAIS EXPECTED THROUGH FRIDAY OF NEXT WEEK. UPPER LEVEL CHANGES WILLBE STRONGER BUT DUE TO THE WEAK MOISTURE AT MID LEVELS UPPER LEVELJET DYNAMICS GET LITTLE CHANCE TO INFLUENCE LOWER LEVELS.

&&

.AVIATION...MOSTLY VFR CONDITIONS EXPECTED ACROSS ALL TAF SITES INTHE MORNING HOURS WITH PASSING SHOWERS ACROSS THE LOCAL AREA. AFTER09/17Z...SCATTERED TO LOCALLY NUMEROUS SHOWERS WITH ISOLD TSRA AREFORECAST TO DEVELOP ACROSS WESTERN PR...AND MAY AFFECT TJMZ. SURFACEWINDS WILL BE FROM THE EAST NORTHEAST WITH SEA BREEZE VARIATIONS ATAROUND 10 TO 15 KTS WITH HIGHER GUSTS AFTER 09/14Z. EXPECTMOUNTAIN OBSCURATIONS THE ENTIRE PERIOD.

&&

.MARINE...SEAS REMAIN AGITATED IN MODERATE TO FRESH TRADE WINDFLOW GENERATED BY HIGHER PRESSURE TO THE NORTH THAT CONTINUESTHROUGH FRIDAY OF NEXT WEEK. SEAS WILL GENERALLY REMAIN BELOW 7FEET HOWEVER SMALL CRAFT SHOULD EXERCISE CAUTION IN ALL BUT THEMOST PROTECTED WATERS. SWELL WILL ARRIVE FROM THE NORTH NORTHWESTAND NORTHEAST DURING THE THROUGH MID WEEK.

Additional Information=========================As expected, vertical wind shear has weaken during the night and intensification is accelerating. Microwave 0046z and 0422z shows an eye building on 85ghz channel.

The system is tracking rather rapidly westwards on the northern edge of the subtropical ridge in the low/mid levels.

Within the next 24 hours system is expected to track west southwestwards decelerating. On and after 36 hours, the steering flow should turn north northwesterly under the influence of a mid-tropospheric ridge building northeast of the system and of a trough southward. Then system should recurve south southeastward. On and after Wednesday, most of the deterministic numerical weather prediction models and ECMWF ensemble prediction system are in good agreement for this meridian track but the spread is yet relatively large. The official track of the RSMC is close to ECMWF.

On this forecast track, upper levels conditions should become very favorable with good outflows especially southward. Sea surface temperatures are favorable over all the forecast period. System should therefore intensify regularly until Friday then begin a slow weakening phase.

At 2:00 PM WST, Tropical Cyclone Victoria (996 hPa) located at 12.3S 102.7E has 10 minute sustained winds of 40 knots with gusts of 55 knots. The cyclone is reported as moving south southeast at 9 knots.

Additional Information=======================Tropical Cyclone Victoria has developed over open waters, well away from Cocos and Christmas Islands.

Microwave imagery overnight showed a small and tight circulation with deep convection wrapping around the low level circulation centre. The vortex was tilted due to northeast wind shear. During Tuesday the system has steadily intensified. A curved band wrap of 0.6 to 0.7 on visible imagery yielded DTs of 3.0 between 0300 and 0600 UTC. Given the initial Dvorak T1.0 classification was made at 0600UTC 8 April, the FT constraint [24hrs after initial T1.0, storm's T-No must be <= T2.5] is being broken. Given the small size of the system and potential for rapid development, this seems appropriate. FT/CI set to 3.0.

Tropical Cyclone Victoria was located using microwave and visible satellite imagery, in particular the TRMM 0221 UTC image.

SSTs and Ocean Heat Potential are conducive for development and there is good poleward outflow due to an approaching upper level trough. Conditions should remain favourable for the next 24 hours or so.

The system is forecast to reach category 2 intensity overnight. Late Wednesday and particularly Thursday, northwest wind shear is forecast to increase and with lower SSTs the system should weaken.

General south to southeast motion is expected under the influence of an upper level ridge to the east and an approaching upper level trough.

The system is not expected to impact Cocos or Christmas Island or the Western Australian mainland. Moderate to heavy rainfall and squally conditions are possible over Christmas Island until Thursday due to the outermost rain bands.

I assume no responsibility for the terminological accuracy of the statements below. I attempt a holistic analysis of the current weather systems across continental North America.

Walda is just exploding right now over Nebraska, in the area where severe thunderstorms were observed early yesterday over Nebraska, Colorado and Kansas. A frontal jet is pumping the convection and sustaining it well into nocturnal hours from Arizona to Colorado, helped by orthographic lift to concentrate a moisture gradient with helicity into the region. EHI values were forecast to be high in the Kansas-Oklahoma region around this time days ago, although we see that the storm is clearly behind. A dry line (?) emanates from Texas over northeast to Missouri, and this is where severe activity may set up for tomorrow. The jet is also creating some upper-troposphere mesoscale folding over Colorado and southwest Nebraska, contributing to the tornadoes despite the cold temperatures in Colorado, barely above freezing. A very strong temperature gradient persists, awakening the tornado season after an almost silent March.

Over east, another mesoscale low has created a brief squall line with an upper trough at the trailing end its warm sector, leading a line of non-severe thunderstorms aided by the evaporative cooling of the lakes and the orthographic instability associated with sunset conditions. The rain showers were almost monsoonal in nature, as we will see over the next few days in Southern Ontario, where up to three or four inches of rain is likely, with some snow possibly to follow. Some fog is filling in behind this line of storms, as cool air overrides the warm surface air that persists in the wake of a multi-day warmup. Near the end of the week, the opposite situation will occur, with cold overriding just above the surface but a warm front keeping the warm-cold gradient nearly vertical. This appears consistently in the GFS solution for Thursday afternoon, when there will be a huge temperature gradient between Southern Ontario and the Allegheny Mountain region, when there could be further mesoscale instability in the lower Ohio River Valley region. Temperatures will continue to fluctuate into the third week of April, when the NAO may trend more positive, and sea ice begins a continuous melt after its recent cracking activity.

Most of the above was prepared by analyzing the satellite image in post #402. This does not include the fog and temperature gradient descriptions. I need to get some sleep.